Spindle motor and hard disk drive including the same

ABSTRACT

There are provided a spindle motor and a hard disk drive including the same. The spindle motor includes: a sleeve installed on a base member and having a circulation hole; a shaft inserted into the sleeve; a rotor hub installed on an upper end of the shaft; and a thrust member installed in an installation groove formed in an upper portion of the sleeve and forming a connection part, the connection part allowing the circulation hole to be in communication with a sealing part formed by the sleeve and the rotor hub and having a liquid-vapor interface of a lubricating fluid disposed therein, wherein the connection part is formed between the sleeve and the thrust member in a circumferential direction, and at least any one part of a radial outer portion of the connection part has an axial gap smaller than that of another part thereof in the circumferential direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No.10-2013-0037734 filed on Apr. 5, 2013, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spindle motor and a hard disk driveincluding the same.

2. Description of the Related Art

Generally, a small spindle motor used in a hard disk drive (HDD) servesto rotate a disk so that a magnetic head is able to write data to thedisk or read data written on the disk.

In addition, the spindle motor is provided with a hydrodynamic bearingassembly, and a bearing clearance formed in the hydrodynamic bearingassembly is filled with a lubricating fluid.

In addition, during rotation of a shaft, the lubricating fluid filled inthe bearing clearance is pumped to form fluid dynamic pressure, therebyrotatably supporting the shaft.

However, pressure lower than atmospheric pressure, that is, negativepressure, may be generated in the bearing clearance due to the pumpingof the lubricating fluid during rotation of the shaft.

In this case, air contained in the lubricating fluid expands, such thatair bubbles are formed. When such air bubbles are introduced to a groovepumping the lubricating fluid, deterioration of rotationalcharacteristics such as the generation of insufficient fluid dynamicpressure, the generation of vibrations, and the like, is caused.

Therefore, a circulation hole for decreasing generation of the negativepressure is formed in a sleeve to suppress the generation of thenegative pressure.

In the following Related Art Document (US 2009-0080819), a configurationin which a circulation hole for decreasing generation of negativepressure is formed to be inclined and connects a bearing clearanceformed by a sleeve and a cover member and a bearing clearance in which aliquid-vapor interface is formed to each other has been used.

However, it is difficult to process the circulation hole and a defect ofthe sleeve may occur at the time of processing the circulation hole.

In addition, even in the case in which the circulation hole is formed,it may still be difficult to discharge air bubbles contained in thelubricating fluid.

RELATED ART DOCUMENT

(Patent Documentt1) US Patent Laid-Open Publication No. 2009-0080819

SUMMARY OF THE INVENTION

An aspect of the present invention provides a spindle motor capable ofdecreasing generation of negative pressure. That is, a spindle motorcapable of easily connecting a sealing part in which a liquid-vaporinterface is disposed and a lower end portion of a bearing clearance toeach other in order to decrease generation of negative pressure isprovided.

An aspect of the present invention also provides a motor capable ofeasily discharging air that may be contained in a lubricating fluid.Particularly, an aspect of the present invention provides a motorcapable of easily discharging air and more reliably removing air thatmay be contained in a lubricating fluid re-circulated to a bearingclearance by allowing the air to be separated from the lubricatingfluid.

Further, an aspect of the present invention provides a motor capable ofeasily discharging air bubbles contained in a lubricating fluid byfacilitating circulation in a circulation hole and capable of easilydischarging air bubbles by decreasing a size of the air bubbles in thecase in which the air bubbles have a large size.

According to an aspect of the present invention, there is provided aspindle motor including: a sleeve fixedly installed on a base member andhaving a circulation hole formed in an axial direction; a shaftrotatably inserted into the sleeve; a rotor hub fixedly installed on anupper end portion of the shaft in the axial direction; and a thrustmember installed in an installation groove formed in an upper portion ofthe sleeve in the axial direction and forming a connection part at thetime of being installed in the installation groove, the connection partallowing the circulation hole to be in communication with a sealing partformed by the sleeve and the rotor hub and having a liquid-vaporinterface of a lubricating fluid disposed therein, wherein theconnection part is formed between the sleeve and the thrust member in acircumferential direction, and at least any one part of a radial outerportion of the connection part has an axial gap smaller than that ofanother part thereof in the circumferential direction.

A transversal cross section of the thrust member in a radial directionmay have a trapezoidal shape.

The thrust member may have an inclined surface, and a facing surface ofthe installation groove disposed to face the inclined surface and theinclined surface may be disposed to be spaced apart from each other by apredetermined distance to form the connection part in the case in whichthe thrust member is installed in the installation groove.

A radial outer portion of a surface of the thrust member forming theconnection part between the thrust member and the sleeve may be providedwith at least one first protrusion protruding toward the sleeve.

An outer portion of a surface of the sleeve in the radial directionforming the connection part between the sleeve and the thrust member maybe provided with at least one second protrusion protruding toward thethrust member.

The first protrusion may have a spiral shape.

The second protrusion may have a spiral shape.

The first protrusion may be provided with a pointed front end portionfirst meeting the lubricating fluid rotated according to rotation of therotor hub.

The second protrusion may be provided with a pointed front end portionfirst meeting the lubricating fluid rotated according to rotation of therotor hub.

According to another aspect of the present invention, there is provideda spindle motor including: a sleeve fixedly installed on a base memberand having a circulation hole formed in an axial direction; a shaftrotatably inserted into the sleeve; a rotor hub fixedly installed on anupper end portion of the shaft in the axial direction; and a thrustmember installed in an installation groove formed in an upper portion ofthe sleeve in the axial direction and forming a connection part at thetime of being installed in the installation groove, the connection partallowing the circulation hole to be in communication with a sealing partformed by the sleeve and the rotor hub and having a liquid-vaporinterface disposed therein, wherein the connection part is formedbetween the sleeve and the thrust member in a circumferential direction,and at least any one part of a radial outer portion of the connectionpart is closed in the circumferential direction.

An outer portion of a surface of the sleeve in the radial direction andthe thrust member forming the connection part may be provided with athird protrusion disposed between the sleeve and the thrust member.

According to another aspect of the present invention, there is provideda hard disk drive including: the spindle motor as described aboverotating a disk by power applied thereto through a substrate; a magnetichead writing data to and reading data from the disk; and a head drivingpart moving the magnetic head to a predetermined position above thedisk.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of thepresent invention will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic cross-sectional view showing a spindle motoraccording to an embodiment of the present invention;

FIGS. 2A and 2B are enlarged views showing the part A of FIG. 1, whereinFIG. 2A shows the case in which a protrusion is provided on a thrustmember and FIG. 2B shows the case in which a protrusion is provided on asleeve;

FIG. 3 is a partially cut-away exploded perspective view showing asleeve and a thrust member included in the spindle motor according tothe embodiment of the present invention;

FIG. 4 is an enlarged view of the part B of FIG. 1;

FIG. 5 is a partially cut-away exploded perspective view showing a rotorhub according to the embodiment of the present invention;

FIG. 6 is a cross-sectional view showing a shaft, a sleeve, and a thrustmember coupled to each other according to the embodiment of the presentinvention;

FIG. 7 is a cross-sectional view corresponding to the line C-C of FIG. 6in the embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view showing a spindle motoraccording to another embodiment of the present invention;

FIG. 9 is an enlarged view of the part D of FIG. 8;

FIGS. 10A through 10D are reference views showing a form in which an airbubble having a large size is divided into air bubbles having a smallsize in the spindle motor according to the embodiment of the presentinvention; and

FIG. 11 is a schematic cross-sectional view of a disk driving deviceusing the spindle motor according to the embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings. The invention may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, the shapes and dimensions ofelements may be exaggerated for clarity, and the same reference numeralswill be used throughout to designate the same or like elements.

FIG. 1 is a schematic cross-sectional view showing a spindle motoraccording to an embodiment of the present invention; FIGS. 2A and 2B areenlarged views showing the part A of FIG. 1, wherein FIG. 2A shows thecase in which a protrusion is provided on a thrust member and FIG. 2Bshows the case in which a protrusion is provided on a sleeve; FIG. 3 isa partially cut-away exploded perspective view showing a sleeve and athrust member included in the spindle motor according to the embodimentof the present invention; FIG. 4 is an enlarged view of the part B ofFIG. 1; FIG. 5 is a partially cut-away exploded perspective view showinga rotor hub according to the embodiment of the present invention; FIG. 6is a cross-sectional view showing a shaft, a sleeve, and a thrust membercoupled to each other according to the embodiment of the presentinvention; and FIG. 7 is a cross-sectional view corresponding to theline C-C of FIG. 6 in the embodiment of the present invention.

Referring to FIGS. 1 through 7, the spindle motor 100 according to theembodiment of the present invention may include a base member 110, asleeve 120, a shaft 130, a rotor hub 140, a thrust member 150, and acover member 160 by way of example.

The spindle motor 100 may be a motor used in a recording disk drivingdevice driving a recoding disk.

Here, terms with respect to directions will be defined. As viewed inFIG. 1, an axial direction refers to a vertical direction, that is, adirection from a lower portion of the shaft 130 toward an upper portionthereof or a direction from the upper portion of the shaft 130 towardthe lower portion thereof, and a radial direction refers to a horizontaldirection, that is, a direction from an outer peripheral surface of therotor hub 140 toward the shaft 130 or from the shaft 130 toward theouter peripheral surface of the rotor hub 140.

In addition, a circumferential direction refers to a rotation directionalong a radius at a predetermined position in the radial direction basedon the center of rotation of the rotor hub 140 or the shaft 130.

The base member 110, which is a fixed member, may configure a stator 20.Here, the stator 20, which means all fixed members except for a rotatingmember, may include the base member 110, the sleeve 120, and the like.

In addition, the base member 110 may include an installation wall part112 having the sleeve 120 inserted thereinto. The installation wall part112 may protrude in an upward axial direction and include aninstallation hole 112 a formed therein so that the sleeve 120 may beinserted thereinto.

In addition, the installation wall part 112 may include a supportsurface 112 b formed on an outer peripheral surface thereof so that astator core 104 may be seated thereon, wherein the stator core 104 has acoil 102 wound therearound. That is, the stator core 104 may be fixedlyinstalled on the outer peripheral surface of the installation wall part112 by an adhesive in a state in which it is seated on the supportsurface 112 b.

However, the stator core 104 may also be installed on the outerperipheral surface of the installation wall part 112 in a press-fittingscheme without using the adhesive. That is, a scheme of installing thestator core 104 is not limited to a scheme of using the adhesive.

In addition, the base member 110 may be manufactured by performingdie-casting using an aluminum (Al) material. Alternatively, the basemember 110 may also be molded by performing plastic working (forexample, press working) on a steel plate.

That is, the base member 110 may be manufactured by various materialsand various processing methods, and is not limited to the base member110 shown in the accompanying drawings.

The sleeve 120, which is a fixed member configuring, together with thebase member 110, the stator 20, may be fixedly installed on the basemember 110 and include a circulation hole 121.

That is, the sleeve 120 may be inserted into and fixed to theabove-mentioned installation wall part 112. In other words, a lower endportion of an outer peripheral surface of the sleeve 120 may be bondedto an inner peripheral surface of the installation wall part 112 by atleast one of an adhesion method, a welding method, and a press-fittingmethod.

In addition, the circulation hole 121 may be extended from a lowersurface of the sleeve 120 in the axial direction and be inclined.Although the case in which the circulation hole 121 is formed in theaxial direction and is inclined has been described by way of example inthe present embodiment, the present invention is not limited thereto.

That is, the circulation hole 121 may also be formed in the radialdirection so as to be parallel with an upper surface of the base member110 and be formed in parallel with the shaft 130 in the axial direction.In addition, the circulation hole may also be configured of two holes,that is, a hole formed in the axial direction and a hole formed in theradial direction.

Meanwhile, the sleeve 120 may include a shaft hole 122 formed therein,wherein the shaft hole 122 has the shaft 130 inserted thereinto. Theshaft 130 may be inserted into the shaft hole 122 and be rotatablysupported by the sleeve 120.

In addition, the sleeve 120 may include a mounting groove 123 formed ata lower end portion thereof, wherein the mounting groove 123 has a covermember 160 installed therein in order to prevent leakage of thelubricating fluid. In addition, at the time of installing the covermember 160 a bearing clearance filled with the lubricating fluid may beformed by an upper surface of the cover member 160 and a lower surfaceof the sleeve 120.

Next, the bearing clearance will be described.

The bearing clearance may indicate a clearance filled with thelubricating fluid. That is, all of the clearance formed by an innerperipheral surface of the sleeve 120 and an outer peripheral surface ofthe shaft 130, the clearance formed by the sleeve 120 and the rotor hub140, the clearance formed by the cover member 160 and the sleeve 120,and the clearance formed by the cover member 160 and the shaft 130 willbe defined as the bearing clearances.

In addition, the spindle motor 100 according to the present embodimentmay have a structure in which the lubricating fluid is filled in all ofthe above-mentioned bearing clearances. This structure may also becalled a full-fill structure.

Meanwhile, the sleeve 120 may have a step groove 124 formed at a lowerend portion thereof. A detailed description of the step groove 124 willbe provided below.

In addition, the sleeve 120 may include upper and lower radial dynamicgrooves 125 and 126 formed in an inner peripheral surface thereof inorder to generate fluid dynamic pressure at the time of rotationaldriving of the shaft 130. In addition, the upper and lower radialdynamic grooves 125 and 126 may be disposed to be spaced apart from eachother by a predetermined distance and have a herringbone or spiralshape.

However, the above-mentioned upper and lower radial dynamic grooves 125and 126 are not limited to being formed in the inner peripheral surfaceof the sleeve 120, but may also be formed in the outer peripheralsurface of the shaft 130.

In addition, the sleeve 120 may have an installation groove 127 formedat an upper end portion thereof, wherein the installation groove 127 hasthe above-mentioned thrust member 150 installed therein. Theinstallation groove 127 may have a shape corresponding to that of thethrust member 150, and one side of the circulation hole 121 may beopened to the bottom surface of the installation groove 127.

A more detailed description of the installation groove 127 will beprovided at the time of describing the thrust member 150.

In addition, the sleeve 120 may have a downwardly inclined surface 128formed on an upper surface thereof, wherein the downwardly inclinedsurface 128 is inclined downwardly toward the shaft hole 121. Thedownwardly inclined surface 128 may be disposed at an inner side of theinstallation groove 127 in the radial direction and serve to allow aninner diameter portion of the rotor hub 140 to be formed at a thickthickness.

The shaft 130, which is a rotating member, may configure a rotor 40.Here, the rotor 40 means a member rotatably supported by the stator 20to thereby rotate.

Meanwhile, the shaft 130 may be rotatably supported by the sleeve 120.In addition, the shaft 130 may include a stopper part 132 formed at alower end portion thereof, wherein the stopper part 132 is inserted intoa step groove 124.

The stopper part 132 may be extended from the lower end portion of theshaft 130 in an outer diameter direction and serve to prevent excessivefloating of the shaft 130 simultaneously with preventing the shaft 130from being separated upwardly from the sleeve 120.

That is, the stopper part 132 may prevent the shaft 130 from beingseparated upwardly from the sleeve 120 due to external impact. Inaddition, the shaft 130 may be floated at a predetermined height at thetime of the rotational driving thereof. At this time, the stopper part132 may serve to prevent the shaft 130 from being excessively floated.

Further, the shaft 130 may have the rotor hub 140 coupled to an upperend portion thereof. To this end, in the case in which the shaft 130 isinstalled in the sleeve 120, the upper end portion of the shaft 130 maybe disposed to protrude upwardly of the sleeve 120.

The rotor hub 140, which is a rotating member configuring, together withthe shaft 130, the rotor 40, may be fixedly installed on the upper endportion of the shaft 130 and rotate together with the shaft 130.

Meanwhile, the rotor hub 140 may include a rotor hub body 142 providedwith an mounting hole 142 a into which the upper end portion of theshaft 130 is inserted, a magnet mounting part 144 extended from an edgeof the rotor hub body 142 in a downward axial direction, and a diskseating part 146 extended from a distal end of the magnet mounting part144 in the outer diameter direction.

In addition, the magnet mounting part 144 may have a driving magnet 144a installed on an inner surface thereof, wherein the driving magnet 144a is disposed to face a front end of the stator core 104 having the coil102 wound therearound.

Meanwhile, the driving magnet 144 a may have an annular ring shape andbe a permanent magnet generating magnetic force having a predeterminedstrength by alternately magnetizing N and S poles in the circumferentialdirection.

Here, rotational driving of the rotor hub 140 will be briefly described.When power is supplied to the coil 102 wound around the stator core 104,driving force capable of rotating the rotor hub 140 may be generated byan electromagnetic interaction between the driving magnet 144 a and thestator core 104 having the coil 102 wound therearound.

Therefore, the rotor hub 140 may rotate. In addition, the shaft 130 towhich the rotor hub 140 is fixedly installed may rotate together withthe rotor hub 140 by the rotation of the rotor hub 140.

Meanwhile, the rotor hub body 142 may be provided with an extension wallpart 142 b extended in the downward axial direction so as to form,together with the outer peripheral surface of the sleeve 120, aninterface F1 between the lubricating fluid and air, that is, aliquid-vapor interface F1.

An inner surface of the extension wall part 142 b may be disposed so asto face the outer peripheral surface of the sleeve 120, and at least oneof the outer peripheral surface of the sleeve 120 and the inner surfaceof the extension wall part 142 b may be inclined so as to form theliquid-vapor interface F1.

That is, at least one of the outer peripheral surface of the sleeve 120and the inner surface of the extension wall part 142 b may be inclinedso as to form the liquid-vapor interface F1 through a capillaryphenomenon.

In addition, both of the outer peripheral surface of the sleeve 120 andthe inner surface of the extension wall part 142 b may be inclined. Inthis case, both of the inclination angles of the outer peripheralsurface of the sleeve 120 and the inner surface of the extension wallpart 142 b may be different from each other.

Meanwhile, a space formed by the inner surface of the extension wallpart 142 b and the outer peripheral surface of the sleeve 120 may becalled a sealing part 106, and the liquid-vapor interface F1 may bedisposed in the sealing part 106.

In addition, an inner diameter portion of the rotor hub body 142 mayinclude a protrusion part 142 c inclined so as to correspond to thedownwardly inclined surface 128 of the sleeve 120.

The protrusion part 142 c may serve to increase an area of an innerperipheral surface of the rotor hub body 142. Therefore, a contact areabetween the rotor hub 140 and the shaft 130 may be increased.

As a result, coupling force between the rotor hub 140 and the shaft 130may be increased due to the increase in the contact area between therotor hub 140 and the shaft 130.

A more detailed description thereof will be provided below. The rotorhub 140 and the shaft 130 may be coupled to each other by an adhesiveand/or press-fitting. In this case, the rotor hub 140 and the shaft 130need to be coupled to each other while having predetermined couplingforce therebetween so as not to be separated from each other even thoughexternal impact is applied thereto.

That is, the inner peripheral surface of the rotor hub body 142 formingthe mounting hole 142 a needs to have an axial length capable ofgenerating the coupling force of a predetermined magnitude or more bycontacting the shaft 130.

To this end, the rotor hub body 142 includes the protruding part 142 c,such that the contact area between the shaft 130 and the rotor hub body142 may be increased. Therefore, the coupling force between the shaft130 and the rotor hub 140 may be further increased.

In addition, the protrusion part 142 c may have a corresponding inclinedsurface 142 d so as to correspond to the downwardly inclined surface 128of the sleeve 120.

Therefore, in the case in which the external impact is applied to therotor hub body 142, damage to the rotor hub body 142 at the innerdiameter portion of the rotor hub body 142 may be further suppressed.

That is, in the case in which a lower surface of the protrusion part 142c is not inclined (for example, in the case in which a transversal crosssection of the protrusion part has a rectangular shape), an edge of theprotrusion part may be easily damaged due to the external impact at thetime of generation of the external impact. In this case, foreignmaterials generated due to the damage are introduced into the bearingclearance, such that rotation characteristics of the shaft 130 may bedeteriorated.

However, since the corresponding inclined surface 142 d of theprotrusion part 142 c and the downwardly inclined surface 128 of thesleeve 120 disposed to face the corresponding inclined surface 142 d ofthe protrusion part 142 c are inclined as described above, the damagemay be decreased at the time of generation of the external impact.Further, the deterioration of the rotation characteristics of the shaft130 may be prevented.

Further, in the case in which the lower surface of the protrusion part142 c is not inclined (for example, in the case in which the transversalcross section of the protrusion part 142 c has the rectangular shape),since a bearing clearance formed by the protrusion part that is notinclined and the sleeve 120 is bent at an angle of 90 degrees, a flow ofthe lubrication fluid may be hindered and a pressure change may begenerated. Therefore, there is a risk that air bubbles will begenerated.

However, since the corresponding inclined surface 142 d of theprotrusion part 142 c and the downwardly inclined surface 128 of thesleeve 120 are inclined as described above, the lubricating fluid maymore easily flow and the pressure change may be decreased.

Further, since external force may be dispersed in a horizontal directionand a vertical direction at the time of the external impact by theinclined protrusion part 142 c, the damage to the rotor hub 140 due tothe external impact may be further decreased.

As described above, even in the case of decreasing a thickness of therotor hub body 142 in order to implement thinness, a decrease in thecontact area between the shaft 130 and the inner diameter portion of therotor hub body 142 is suppressed by the protrusion part 142 c, whereby adecrease in the coupling force between the shaft 130 and the rotor hub140 may be prevented. Therefore, separation between the shaft 130 andthe rotor hub 140 due to the external impact may be prevented.

In addition, the corresponding inclined surface 142 d of the protrusionpart 142 c is inclined, whereby the damage to the rotor hub body 142 maybe decreased, the lubricating fluid may more easily flow, and thepressure change may be decreased.

Meanwhile, although the case in which the corresponding inclined surface142 d of the protrusion part 142 c and the downwardly inclined surface128 of the sleeve 120 are inclined at the same angle to thereby bedisposed in parallel with each other has been described by way ofexample in the present embodiment, the present invention is not limitedthereto.

That is, the corresponding inclined surface 142 d and the downwardlyinclined surface 128 may be inclined so as to have different gradients.

The thrust member 150 may be a fixed member configuring, together withthe base member 110 and the sleeve 120, the stator 20. In addition, thethrust member 150 may be installed in the installation groove 127 of thesleeve 120 and form a connection part 170 connected to the circulationhole 121 at the time of being installed in the installation groove 127.

The connection part 170 may be formed by the sleeve 120 and the rotorhub 140 and serve to allow the sealing part 106 in which theliquid-vapor interface F1 is disposed to be in communication with thecirculation hole 121. A detailed description thereof will be providedbelow.

Meanwhile, a thickness of an inner diameter portion of the thrust member150 (an axial length of the inner diameter portion of the thrust member150) may be different from that of an outer diameter portion thereof(that is, an axial length of the outer diameter portion thereof).

As an example, a transversal cross section of the thrust member 150 mayhave an approximately trapezoidal shape. More specifically, a radiallength of an upper end portion of the thrust member 150 may be longerthan that of a lower end portion thereof. In addition, the thrust member150 may have a constant inner diameter.

In addition, the thrust member 150 may have an inner peripheral surfacecontacting an inner wall surface of the installation groove 127 and alower surface contacting the bottom surface of the installation groove127. Further, the thrust member 150 may include an inclined surface 152extended from the lower surface thereof.

As described above, the transversal cross section of the thrust member150 has the approximately trapezoidal shape, whereby damage to thethrust member 150 may be decreased at the time of external impact.

Meanwhile, in the case in which the thrust member 150 is installed inthe installation groove 127, a facing surface 127 a of the installationgroove 127 disposed to face the inclined surface 152 and the inclinedsurface 152 may be disposed to be spaced apart from each other by apredetermined distance to form the connection part 170.

As described above, in the case in which the thrust member 150 isinstalled on the sleeve 120, the thrust member 150 and the sleeve 120may form the connection part 170 to connect the circulation hole 121 andthe sealing part 106 to each other.

As a result, since the bearing clearance formed by the sleeve 120 andthe cover member 160 and the sealing part 106 are in communication witheach other only by installing the thrust member 150 on the sleeve 120,generation of negative pressure may be decreased.

In other words, since the bearing clearance formed by the sleeve 120 andthe cover member 160 and the sealing part 106 are in communication witheach other by the circulation hole 121 and the connection part 170, thegeneration of the negative pressure in the bearing clearance formed bythe sleeve 120 and the cover member 160 may be decreased.

Furthermore, air bubbles generated in the bearing clearance may be moresmoothly discharged to the outside of the bearing clearance.

In addition, a component for decreasing the generation of the negativepressure may be more easily formed as compared with the case in whichonly the circulation hole is formed so that the bearing clearance formedby the sleeve 120 and the cover member 160 and the sealing part 106 arein communication with each other. That is, in the case in which thecirculation hole is formed so that the bearing clearance formed by thesleeve 120 and the cover member 160 and the sealing part 106 are incommunication with each other, generation of a defect in manufacturingthe sleeve 120 may be decreased.

Further, the connection part 170 may be formed in the circumferentialdirection between the sleeve 120 and the thrust member 150, and at leastany one part of a radial outer portion of connection part 170 may havean axial gap smaller than that of another part thereof in thecircumferential direction. That is, the radial outer portion of theconnection part 170 may be provided with at least one part having anaxial gap smaller as compared with another part.

In other words, a radial outer portion of the inclined surface 152 ofthe thrust member 150 forming the connection part 170 between the thrustmember 150 and the sleeve 120 may be provided with at least one firstprotrusion 156 protruding toward the sleeve 120. Alternately, a radialouter portion of the facing surface 127 a of the installation groove 127of the sleeve 120 forming the connection part 170 between the sleeve 120and the thrust member 150 may be provided with at least one secondprotrusion 129 protruding toward the thrust member 150. Here, the firstprotrusion 156 may be provided integrally with the thrust member 150 orbe attached as a separate member to the thrust member 150. In addition,the second protrusion 129 may be provided integrally with the sleeve 120or be attached as a separate member to the sleeve 120.

Therefore, the radial outer portion of the connection part 170 may beprovided with at least one part having an axial gap smaller than anotherpart in the circumferential direction by the first or second protrusion156 or and 129.

Meanwhile, the first or second protrusion 156 or 129 may have a spiralshape. Further, the first or second protrusion 156 or 129 may beprovided with a pointed front end portion 156 a or 129 a first meetingthe lubricating fluid rotated according to the rotation of the rotor hub140. That is, the front end portion 156 a or 129 a of the first orsecond protrusion 156 or 129 may have a very small width in the radialdirection.

Here, the connection part 170 may be continuously or discontinuouslyformed in the circumferential direction.

When the connection part having the above-mentioned configuration isformed, even though a size of an air bubble formed by air is large, thesize of the air bubble may be decreased by the first or secondprotrusion 156 or 129. In addition, since a cross-sectional area of theconnection part 170 in the circumferential direction is decreased at theradial outer portion of the connection part 170 by the first or secondprotrusion 156 or 129, the lubricating fluid may be easily circulated.As a result, the air bubbles contained in the lubricating fluid may beeasily discharged.

A mechanism of decreasing a size of an air bubble according to theembodiment of the present invention will be described with reference toFIGS. 10A through 10D.

First, when the rotor hub 140 is rotated, rotational force is applied tothe lubricating fluid according to the rotation of the rotor hub 140,such that the lubricating fluid may be rotated together with the rotorhub 140. Therefore, as shown in FIG. 10B, an air bubble ab contained inthe lubricating fluid may be rotated together with the lubricating fluidin the circumferential direction.

The air bubble ab rotated together with the lubricating fluid may meetthe front end portion 156 a or 129 a of the first or second protrusion156 or 129 (See FIG. 10C). In this case, when a size of the air bubbleab is small, the air bubble ab may be directed toward in the innerdiameter direction of the outer diameter direction based on the frontend portion 156 a or 129 a. However, in the case in which the size ofthe air bubble ab is large to some degree, the air bubble may beseparated into two air bubbles having a small size by the front endportion 156 a or 129 a (See FIG. 10C).

In this process, the air bubble ab directed toward the outer diameterdirection based on the front end portion 156 a or 129 a may be naturallydischarged to the outside of the connection part 170 (See FIG. 10D). Anair bubble directed toward the inner diameter direction based on thefront end portion 156 a or 129 a repeatedly passes through the front endportion 156 a or 129 a, such that it may be discharged to the outside.

As a result, at least one first or second protrusion 156 or 129 may beprovided at the radial outer portion of the connection part 170 todecrease the size of the air bubble ab, in order words, suppressexcessive growth of the air bubble or decrease the cross-sectional areaof the connection part 170 in the circumferential direction at theradial outer portion of the connection part 170, thereby facilitatingcirculation of the lubricating fluid. Therefore, the air bubblecontained in the lubricating fluid may be easily discharged.

Meanwhile, the thrust member 150 may be bonded to the installationgroove 127 of the sleeve 120 by an adhesive. In addition, a groove inwhich the adhesive may be filled may be formed at an edge at which theinner wall surface and the lower surface of the installation groove 127meet each other to increase coupling force between the thrust member 150and the sleeve 120. The thrust member 150 may also be coupled to theinstallation groove 127 by a method such as a press-fitting method, awelding method, or the like.

In addition, the thrust member 150 may be formed of a material differentfrom that of the sleeve 120. That is, the thrust member 150 may beformed of a material having excellent abrasion resistance.

However, the present invention is not limited thereto. That is, thethrust member 150 and the sleeve 120 may also be formed of the samematerial. In this case, outer surfaces of the thrust member 150 and thesleeve 120 may be coated with different materials. That is, the outersurface of the thrust member 150 may also be coated with a material forimproving the abrasion resistance.

Meanwhile, a thrust dynamic groove 154 may be formed in an upper surfaceof the thrust member 150. However, the thrust dynamic groove 154 is notlimited to being formed in the upper surface of the thrust member 150,but may also be formed in the rotor hub.

The cover member 160, which is a fixed member configuring, together withthe base member 110, the sleeve 120, and the thrust member 150, thestator 20, may be fixedly installed on a lower surface of the sleeve 120to prevent leakage of the lubricating fluid.

That is, the cover member 160 may be bonded to the mounting groove 123of the sleeve 120 by at least one of an adhering method and a weldingmethod.

Hereinafter, a spindle motor according to another embodiment of thepresent invention will be described with reference to the accompanyingdrawings. However, components that are the same as the componentsincluded in the spindle motor according to the embodiment of the presentinvention described above will be denoted by the same referencenumerals, and an illustration and a detailed description thereof will beomitted.

FIG. 8 is a schematic cross-sectional view showing a spindle motoraccording to another embodiment of the present invention; FIG. 9 is anenlarged view of the part D of FIG. 8; and FIGS. 10A through 10D arereference views showing a form in which an air bubble having a largesize is divided into air bubbles having a small size in the spindlemotor according to the embodiment of the present invention.

Referring to FIGS. 8 through 10D, the spindle motor 200 according toanother embodiment of the present invention is different from thespindle motor 100 according to the embodiment of the present inventionin which the radial outer portion of the connection part 170 is providedwith at least one part having the axial gap smaller than that of anotherpart in the circumferential direction, in that at least any one part ofthe radial outer portion of the connection part 170 is closed in thecircumferential direction.

That is, the spindle motor 100 according to the embodiment of thepresent invention may include the first or second protrusion 156 or 129formed at a radial outer edge of the connection part 170 to decrease anaxial gap of the connection part 170. On the other hand, the spindlemotor 200 according to another embodiment of the present invention maybe different from the spindle motor 100 according to the embodiment ofthe present invention in that a radial outer edge of the connection part170 is provided with a third protrusion 175 closing the entire axiallength of the connection part 170.

In this case, the third protrusion 175 is fixed to both of the thrustmember 150 and the sleeve 120, such that an axial gap may not be formed.Here, the third protrusion 175 may be provided integrally with at leastany one of the thrust member 150 and the sleeve 120 or be attached as aseparate member to the thrust member 150 and the sleeve 120.

Similar to the embodiment of the present invention, also in this case,the third protrusion 175 may have a spiral shape. Further, the thirdprotrusion 175 may be provided with a pointed front end portion 175 afirst meeting the lubricating fluid rotated according to the rotation ofthe rotor hub 140. That is, the front end portion 175 a of the thirdprotrusion 175 may have a very small width in the radial direction.

Here, the connection part 170 may be continuously or discontinuouslyformed in the circumferential direction.

When the connection part having the above-mentioned configuration isformed, even though a size of an air bubble formed by air is large, thesize of the air bubble may be decreased by the third protrusion 175. Inaddition, since a cross-sectional area of the connection part 170 in thecircumferential direction is decreased at the radial outer portion ofthe connection part 170 by the third protrusion 175, the lubricatingfluid may be easily circulated. As a result, the air bubbles containedin the lubricating fluid may be easily discharged.

In addition, referring to FIGS. 10A through 10D, the mechanism ofdecreasing a size of an air bubble in the spindle motor 100 according tothe embodiment of the present invention described above may be similarlyapplied to the spindle motor 200 according to another embodiment of thepresent invention.

First, when the rotor hub 140 is rotated, rotational force is applied tothe lubricating fluid according to the rotation of the rotor hub 140,such that the lubricating fluid may be rotated together with the rotorhub 140. Therefore, as shown in FIG. 10B, an air bubble ab contained inthe lubricating fluid may be rotated together with the lubricating fluidin the circumferential direction.

The air bubble ab rotated together with the lubricating fluid may meetthe front end portion 175 a of the third protrusion 175 (See FIG. 10C).In this case, when a size of the air bubble ab is small, the air bubbleab may be directed toward in the inner diameter direction of the outerdiameter direction based on the front end portion 175 a. However, in thecase in which the size of the air bubble ab is large to some degree, theair bubble may be separated into two air bubbles having a small size bythe front end portion 175 a (See FIG. 10C).

In this process, the air bubble ab directed toward the outer diameterdirection based on the front end portion 175 a may be naturallydischarged to the outside of the connection part 170 (See FIG. 10D). Anair bubble directed toward the inner diameter direction based on thefront end portion 175 a repeatedly passes through the front end portion175 a, such that it may be discharged to the outside.

As a result, at least one third protrusion 175 may be provided at theradial outer portion of the connection part 170 to decrease the size ofthe air bubble ab, in order words, suppress excessive growth of the airbubble or decrease the cross-sectional area of the connection part 170in the circumferential direction at the radial outer portion of theconnection part 170, thereby facilitating circulation of the lubricatingfluid. Therefore, the air bubble contained in the lubricating fluid maybe easily discharged.

Referring to FIG. 11, a recording disk driving device 800 having thespindle motor 100 or 200 according to the present invention mountedtherein may be a hard disk drive and include the spindle motor 100 or200, a head transfer part 810, and a housing 820.

The spindle motor 100 or 200 may have all features of the motoraccording to he present invention described above and have a recordingdisk 830 mounted thereon.

The head transfer part 810 may transfer a head 815 detecting informationof the recording disk 830 mounted in the spindle motor 100 or 200 to asurface of the recording disk of which the information is to bedetected.

Here, the head 815 may be disposed on a support part 817 of the headtransfer part 810.

The housing 820 may include a motor mounting plate 822 and a top cover824 shielding an upper portion of the motor mounting plate 822 in orderto form an internal space receiving the spindle motor 100 or 200 and thehead transfer part 810 therein.

As set forth above, according to the embodiments of the presentinvention, a spindle motor capable of decreasing generation of negativepressure may be provided. That is, a spindle motor capable of easilyconnecting a sealing part in which a liquid-vapor interface is disposedand a lower end portion of a bearing clearance to each other in order todecrease generation of negative pressure may be provided.

In addition, according to the embodiment of the present invention, amotor capable of easily discharging air that may be contained in alubricating fluid may be provided. Particularly, according to theembodiments of the present invention, air is easily separated from thelubricating fluid, whereby the air may be easily discharged and air thatmay be contained in a lubricating fluid re-circulated to a bearingclearance may be more reliably removed.

Further, circulation in a circulation hole is facilitated, whereby anair bubble contained in a lubricating fluid may be easily discharged,and a size of the air bubble is decreased in the case in which the airbubble has a large size, whereby the air bubble may be easilydischarged.

While the present invention has been shown and described in connectionwith the embodiments, it will be apparent to those skilled in the artthat modifications and variations can be made without departing from thespirit and scope of the invention as defined by the appended claims.

What is claimed is:
 1. A spindle motor comprising: a sleeve fixedlyinstalled on a base member and having a circulation hole formed in anaxial direction; a shaft rotatably inserted into the sleeve; a rotor hubfixedly installed on an upper end portion of the shaft in the axialdirection; and a thrust member installed in an installation grooveformed in an upper portion of the sleeve in the axial direction andforming a connection part at the time of being installed in theinstallation groove, the connection part allowing the circulation holeto be in communication with a sealing part formed by the sleeve and therotor hub and having a liquid-vapor interface of a lubricating fluiddisposed therein, wherein the connection part is formed between thesleeve and the thrust member in a circumferential direction, and atleast any one part of a radial outer portion of the connection part hasan axial gap smaller than that of another part thereof in thecircumferential direction.
 2. The spindle motor of claim 1, wherein atransversal cross section of the thrust member in a radial direction hasa trapezoidal shape.
 3. The spindle motor of claim 2, wherein the thrustmember has an inclined surface, and a facing surface of the installationgroove disposed to face the inclined surface and the inclined surfaceare disposed to be spaced apart from each other by a predetermineddistance to form the connection part in the case in which the thrustmember is installed in the installation groove.
 4. The spindle motor ofclaim 1, wherein a radial outer portion of a surface of the thrustmember forming the connection part between the thrust member and thesleeve is provided with at least one first protrusion protruding towardthe sleeve.
 5. The spindle motor of claim 1, wherein an outer portion ofa surface of the sleeve in the radial direction forming the connectionpart between the sleeve and the thrust member is provided with at leastone second protrusion protruding toward the thrust member.
 6. Thespindle motor of claim 4, wherein the first protrusion has a spiralshape.
 7. The spindle motor of claim 5, wherein the second protrusionhas a spiral shape.
 8. The spindle motor of claim 4, wherein the firstprotrusion is provided with a pointed front end portion first meetingthe lubricating fluid rotated according to rotation of the rotor hub. 9.The spindle motor of claim 5, wherein the second protrusion is providedwith a pointed front end portion first meeting the lubricating fluidrotated according to rotation of the rotor hub.
 10. A hard disk drivecomprising: the spindle motor of claim 1 rotating a disk by powerapplied thereto through a substrate; a magnetic head writing data to andreading data from the disk; and a head driving part moving the magnetichead to a predetermined position above the disk.
 11. A spindle motorcomprising: a sleeve fixedly installed on a base member and having acirculation hole formed in an axial direction; a shaft rotatablyinserted into the sleeve; a rotor hub fixedly installed on an upper endportion of the shaft in the axial direction; and a thrust memberinstalled in an installation groove formed in an upper portion of thesleeve in the axial direction and forming a connection part at the timeof being installed in the installation groove, the connection partallowing the circulation hole to be in communication with a sealing partformed by the sleeve and the rotor hub and having a liquid-vaporinterface disposed therein, wherein the connection part is formedbetween the sleeve and the thrust member in a circumferential direction,and at least any one part of a radial outer portion of the connectionpart is closed in the circumferential direction.
 12. The spindle motorof claim 11, wherein an outer portion of a surface of the sleeve in theradial direction and the thrust member forming the connection part isprovided with a third protrusion disposed between the sleeve and thethrust member.